Heat treating furnace



Oct. 8, 1957 c. PETERSON 2,809,027

HEAT TREATING FURNACE Filed Nov. 1s, 195e nrt @uw um A ToRN/SY UnitedStates Patent fi HEAT TREATING FURNACE Charles L. Peterson, Cicero,Ill., assignor to Western Electric Company, Incorporated, New York, N.Y., a corporation of New York Application November 13, 1956, Serial No.621,32

6 Claims. (Cl. 263-42) This invention relates to heat treating apparatusand more particularly to an electric furnace for performing drying,baking, hardening, annealing, and tempering operations and otheroperations of a similar nature.

In the present invention, the disclosed apparatus is described asutilized to anneal spools of wire, but it will be manifest from thefollowing description that the invention is equally applicable to,various heat treatments of other types of work pieces.

In the manufacture of electrical conductors, large metal rods aregenerally drawn down to the desired wire size by means of wire drawingmachines. When these wire drawing operations have been completed, thewire is in a work hardened state. Wire in this state does not have theability to withstand repeated ilexings without cracking which isgenerally required in electrical conductors. The wire must then beuniformly annealed to render it less brittle and hence suitable for useas an electrical conductor.

It is therefore a principal object of this invention to provide a heattreating apparatus which will heat work pieces uniformly throughout.

It is another object of this invention to provide a furnace which willrapidly and uniformly apply heated gases from a predetermined pattern ofheating tubes to anneal spools of wire.

Another object of this invention is to provide a convection typeannealing furnace in which the work being annealed does not project intothe heating unit but is heated by a gas exiting from a plurality ofuniformly spaced gas heating tubes.

With these and other objects in View, the present inven tioncontemplates a convection type furnace including a heating chamber forcontaining work to be heat treated forming a part of a closed circuitfor confining a gas and a convection blower for circulating the gasthroughout the closed circuit. Heaters are provided for radiantlyheating a portion of the closed circuit to impart heat to thecirculating gas.

Other objects, advantages, and features of the invention will becomeapparent upon consideration of the following detailed description inconjunction with the accompanying drawings wherein:

Fig. l is an elevation view, in full section, of a heat treating furnaceembodying the principal features of the invention;

Fig. 2 is a sectional view taken along the line 2-2of Fig. 1illustrating the arrangement of the gas heating tubes which providesuniform temperatures at all points in planes parallel to the base of theapparatus; and

Fig. 3 is a sectional View taken along the line 3-3 of Fig. 1illustrating a plurality of spools of wire resting on the open grillworkwhich supports the work within the heating chamber. l

Attention now is directed to the drawings wherein like numerals ofreference designate like parts throughout the several views and whereina base 1l is provided with a through the tubes.

convection blower 12. The base 11 is further provided with a pluralityof posts 14 which support an apertured baflle plate 15 and worksupporting grillwork 16 in spaced relationship above the base.

A work heating chamber, designated generally by the reference numeral17, rests upon the base. This charnber comprises a metal inner bailllechamber 19 and an outer shell 2@ of refractory material; both held inconcentric relationship by a metal cover plate 21 to which they aresecured. A metal sealing ring 22 depends from the lower extremity of theshell 20. This ring projects into a sealing liquid 24 within a sealingtrough 25 fixed to the base 11 and thereby provides a gas tight seal.The outer shell 20 is further provided with hooks 26 or the like topermit attachment of any suitable means for raising and lowering thework heating chamber i7 to permit the furnace to be loaded and unloaded.

A plurality of return bend radiant heating tubes 27 are secured withinapertures in the cover plate 21. First extremities 29 of these tubesconnect with a passage 30 created by the concentric relationship of thebaffle chamber 19 and outer shell 20. The second extremities 31 of thetubes 27 open into the top of the baffle chamber 19 formed by the coverplate 21. Attention is particularly directed to the uniform arrangementof the exit ends 31 of the tubes 27 into two concentric squareswhereinthere is equal spacing between the exit ends in each square.

A gas heating bell, designated generally by the reference numeral 32,rests atop the Work heating chamber i7. The interior of the gas heatingbell 32 is provided with a plurality of vertically depending radiantelectric heating elements 34 which are energized by any suitable means.The gas heating bell is further provided with a hook 35 secured to thetop thereof to which may be attached any suitable means for raising andlowering the bell.

Operation In order that a better understanding of the invention may behad, its mode of operation during a typical annealing process will nowbe described. The work to be annealed is rst placed upon the opengrillwork 16 in an orderly manner and uniformly distributed over the topof the grillwork. In the drawings, the work to be annealed has beenillustrated as spools of wire 36, which are resting upon the grillwork16; only one layer of spools being shown for purposes of clarity., Thework heating cham* ber 17 is then lowered to the position shown inFig. 1. In this position, the sealing ring 22 is partially immersed inthe sealing liquid 24 and a gas tight seal is formed between the workheating chamber 17 and the base 11. Additionally, when the heatingchamber 17 is in this position, a closed gas circuit is formed which isbounded by the walls of outer refractory shell 20, the walls of thebaille chamber 19, the walls of the tubes 27 and the top of the base 11.

The next step is to lower the gas heating bell 32 into the positionshown in Fig. l and energize the heating elements 34. When thetemperature of the heating elements begins to rise, the convectionblower 12 is started. The blades of the blower are so shaped that theyforce the gas within the heating chamber 17 laterally across the face ofthe base 11, up the passage 30 and into the rst extremities 29 of theradiant heating tubes 27. From there, the gas moves through the tubes27, into the interior of the baille chamber 17, through and around thework, and finally it passes through the aperture in the baille plate 15to the convection blower 12. As the temperature of the heating elements34 rises, these elements radiate heat and thus elevate the temperatureof the radiant heating tubes 27. This heat is transferred to the gas asit passes The hot gas then transfers heat to the work 36 as it passesaround the work and thereby eilects the annealing of the work.

The concentric square configuration of the tube exits permits the tubesto project uniformly spaced jets of heated gas into the chamber and as aresult each jet supplies the same volume of heated gas to the chamber.As the heated gas advances toward the work, each portion of eachcross-sectional area of the heating chamber is maintained at the sameeven heat. With the present arrangement of jets, uniform gasdistribution is attained throughout the interior of the baille chamber19 and as a consequence there is uniform annealing of the work.

The temperature to which the gas is elevated and the length of time forwhich the work remains within the furnace are, of course, dependent uponthe nature of the work. When the proper time has elapsed, the heatingbell 32 and then the heating chamber 17 are raised and the workpermitted to cool.

It is to be understood that the above-described arrangements are simplyillustrative of the application of the prin ciples of this invention.Numerous other arrangements may be readily devised by those skilled inthe art which will embody the principles of the invention and fallwithin the spirit and scope thereof.

What is claimed is:

l. A heat treating furnace comprising a base, means for supporting workpieces above said base, a heating chamber adapted to cooperate with saidbase to form a gas tight enclosure, a baille chamber concentrically seucured within said heating chamber to form a gas passage therebetween, aplurality of return bend tubes secured to one end of the heating chamberand interconnecting said baille chamber and said passage, means forforcing circulation of a gas through said passage, said tubes, and saidbaille chamber, and means for heating the gas circulating through thetubes.

2. A heat treating furnace comprising a base, means for supporting workpieces above said base, a double walled heating chamber having aperforated end -supporting said walls in concentric relationship andadapted to surround said supporting means when resting on said base,means on the exterior wall of said chamber and on said base for forminga gas tight seal therebetween, a plurality of return bend tubespositioned in the perforations in the end of said chamber andinterconnecting the interior of said chamber and the passage formedbetween the double walls of said chamber, means for forcing circulationof a gas through said passage and said tubes and into contact withworkpieces Vsupported within the interior of said chamber, and means forheating the gas circulating through said tubes.

3. A heat treating furnace comprising a base, an open grillwork forsupporting work pieces above said base, a bell-shaped heating chamberadapted to surround said grillwork when resting on said base, means onsaid chamber and said base for forming a gas tight seal therebetween, abaille depending from the end of said chamber toward the open endthereof, said baille being adapted to fit closely around said supportinggrillwork and terminating in an open end spaced inwardly from the planeof the open end of said chamber, a plurality of return bend tubespositioned in apertures in the closed end of said chamber forinterconnecting the interior of said baille and the passage formedbetween the walls of said baille and the walls of said chamber, aconvection blower for circulating a gas through said passage, saidtubes, and said baille, and a heater adapted to surround said tubes whenresting on said Ybase for heating the gas circulating through the tubes.

4. A heat treating furnace comprising a base, an apertured baille platefixed in spaced relationship above said base, an open grillwork forsupporting work pieces fixed in spaced relationship above said bailleplate, a bellshaped heating chamber having a plurality of aperturesformed in the closed end thereof and adapted to enclose said grillworkwhen resting on said base, means on said heating chamber and said basefor forming a gas tight seal therebetween, a baille chamberconcentrically secured within said heating chamber and forming a gaspassage therebetween, said baille chamber being adapted to fit closelyabout said grillwork and spaced away from the base when the heatingchamber is resting on said base, a plurality of return bend tubespositioned in said apertures in the closed end of said heating chamberfor connecting the gas passage with the interior of the baffle chamber,a convection blower secured to the underside of said base with theblades thereof interposed between said base and said baille plate forforcing circulation of a gas throughout the circuit defined by the gaspassage, the tubes, the interior of said baille chamber, and the spacebetween the baille plate and base, a bell-shaped housing adapted tosurround said tubes when resting on the closed end of said heatingchamber, and a pfuraliiy of heating elements secured within said housingfor radiantly heating said tubes to elevate the temperature of the gascirculating therethrough.

5. A heat treating furnace comprising a base, means for supporting workpieces above said base, a heating chamber adapted to cooperate with saidbase to form a gas tight enclosure, a baffle chamber concentricallysecured within said heating chamber to form a gas passage therebetween,a first group of return bend tubes secured to the closed end of saidheating chamber extending from apertures opening on the space betweenthe walls of the heating and baille chambers and terminating in exitapertures that are equally spaced to define a square pattern within theconfines of the baille chamber, a second group of return bend tubesextending from additional apertures opening on the space between thewalls of the heating and baille chambers and terminating in exitapertures that are equally spaced to define a second square patternwithin said iirst square pattern and spaced therefrom a distancesubstantially equal to the distance between any two adjacent exitapertures in said first and second pattern, means for forcingcirculation of a gas through said passage, said tubes, and said baillechamber, and means for heating the gas circulating through the tubes.

6. A heat treating furnace comprising a base, an apertured baille platefixed in spaced relationship above said base, an open grillwork forsupporting work pieces fixed in spaced relationship above said bailleplate, a bellshaped heating chamber having a plurality of aperturesformed Vin the closed end thereof and adapted to enclose said grillworkwhen resting on said base, means on said heating chamber and said basefor forming a gas tight seal therebetween, a baille chamberconcentrically secured within said heating chamber and forming a gaspassage therebetween, said baille chamber being adapted to fit closelyabout said grillwork and spaced away from the base when the heatingchamber is resting on the base, a first group of return .bend tubessecured to the closed end of said heating chamber extending from theapertures opening on Vthe space between the walls of the heating andbaille chambers and terminating in exit apertures that are equallyspaced to define a square pattern within the confines of the baillechamber, a second group of return bend tubes extending from additionalapertures opening on the space between the walls of the heating and bafechambers and terminating in exit apertures that are equally spaced todefine a second square pattern within said first square pattern andspaced therefrom a distance substantially equal to the distance betweenany two adjacent exit apertures in said first and second pattern, aconvection blower secured to the underside of said base with the bladesthereof interposed between said base and said baille plate for forcingcirculation of a gas throughout the circuit defined by the gas passage,the tubes, the interior of the baille chamber, and the space between thebaille plate and base, a bell-shaped housing adapted to surround saidtubes when resting on the closed end of References Cited in the file ofthis patent said heatiug ehamher, and'a plurality uf heating elementsUNITED STATES PATENTS secured withm sa1d housmg for radlantly heatlngsaid tubes to elevate the temperature of the gas circulating 2276971Hoak Mar' 17 1942 therethrough. 5 2,341,962 Tanner Feb. 15, 19442,495,561 Wilson Ian. 24, 1950

